Research On Safety Risk Management On Deep Pit Excavationof Subway Station Of Lanzhou Rail Transit

In recent years,urbanization process is becoming obvious,this is from the facts that more and more rural people gather to cities,a large numbers of public buildings,houses and facilities are simultaneously constructed.In order to alleviate the problem of traffic congestion and solve the high population density,some cities have adopted measurements,such as construction of elevated overpasses and development underground spaces,between which the construction of subway is the most effective way.The urban rail transit has lots of advantages,i.e.,high efficiency,convenience,low pollution and low energy consumption,which greatly improves the efficiency of urban transportation,promotes the whole social environment,and plays an important role in the sustainable development of society.In the planning and selection of rail transit lines,the subway station will give priority to the factors,i.e.,people gathering,traffic density,and economic development,etc.,so most subway stations are chose to the places with dense people and convenient existing traffic,which are generally close to existing pipelines,roads,and structures.Consequently,In the construction of rail transit,there are many problems of deep foundation pit.Therefore,it is great importance to accurately risk assess,dynamically control and effectively risk reduce of the deep foundation pits during the construction of subway stations.The risk research on deep foundation pits construction can provide the theoretical basis and engineering experience for similar deep foundation pit construction.Risk management of subway station starts from research stage to delivery and operation stage,which is a full and complete coverage process.Therefore,this article comprehensively reviews the current safety risk of subway station construction at home and abroad.Then the station construction process was divided into the whole engineering,unit engineering,divisional and sub-divisional works and procedure.We follow the following process,e.g.risk identification,assessment and control.Using the WBS-RBS based specialists method to obtain the risk indexes of each procedure.Then AHP is used to calculate the risk indexes of the upper layer.Finally,the overall risk indexes of the safety risk of deep foundation pit construction for subway station were obtained and the safety risk assessment system of deep foundation pit construction for subway station were built up.Take the Youdian Dalou Station(first-stage project of Lanzhou Rail Transit Line 2)for example,we proposed a risk control model from risk identification,risk assessment,management and control.We also test the new model and optimize the model during the practice process for achieving a reasonable,effective and reliable purpose.Based on the PDCA method in the quality management,the model proposed in this paper is cycled by the orders of identification(plan),evaluation(implementation),control(check)and validation(processing).In detail,the tasks in the construction process of subway stations are decomposed and identified firstly.Then,the index weight of each task decomposition layer is calculated using the analytic hierarchy process.At the same time,the overall risk and major risk of the deep foundation pit of the stations are obtained combined with the expert evaluation(score),and targeted control are proposed according to the evaluation results.Finally,it is applied to the risk control of practical engineering(Youdian Building Station)to verify the reliability of the evaluation management model.